Request-Response Procedure for Wireless Network

ABSTRACT

This document provides a solution where a requesting wireless apparatus indicates in a probe request message that the requesting wireless apparatus supports a collision avoidance mechanism that enables a responding wireless apparatus to reduce a number probe response messages by responding to a plurality of probe response messages with a single probe response message.

FIELD

The invention relates to the field of radio communications and,particularly, to a request-response procedure in a wireless network.

BACKGROUND

Some wireless networks utilize active scanning in which a scanningdevice probes for other devices by transmitting a request message whichobliges a responding device to respond. In the response, the scanningdevice gains information on the wireless network(s) available. Such arequest-response procedure may be used as a preliminary procedure for aconnection establishment.

BRIEF DESCRIPTION

According to an aspect of the present invention, there is provided amethod comprising: acquiring, in a wireless apparatus a plurality ofprobe request messages originated from a plurality of requestingwireless apparatuses, each of the plurality of probe request messagescomprising an information element that indicates that each of theplurality of requesting wireless apparatuses supports a collisionavoidance mechanism; and in response to detecting that said informationelement comprised in the plurality of probe request messages andindicating said support for the collision avoidance mechanism, causingtransmission of a probe response message that responds to the pluralityof probe request messages.

According to another aspect of the present invention, there is provideda method comprising: causing, in a requesting wireless apparatus,transmission of a probe request message from the requesting wirelessapparatus, wherein the probe request message comprises an informationelement that indicates that the requesting wireless apparatus supports acollision avoidance mechanism that enables a responding wirelessapparatus to reduce a number probe response messages by responding to aplurality of probe response messages with a single probe responsemessage; and acquiring, in the requesting wireless apparatus, a proberesponse message transmitted by a responding wireless apparatus as aresponse to the probe request message.

According to another aspect of the present invention, there is providedan apparatus comprising: at least one processor; and at least one memoryincluding program instructions. The at least one memory and the computerprogram code are configured, with the at least one processor, to causethe apparatus to acquire a plurality of probe request messagesoriginated from a plurality of requesting wireless apparatuses, each ofthe plurality of probe request messages comprising an informationelement that indicates that each of the plurality of requesting wirelessapparatuses supports a collision avoidance mechanism; and in response todetecting said information element comprised in the plurality of proberequest messages and indicating said support for the collision avoidancemechanism, cause transmission of a probe response message that respondsto the plurality of probe request messages.

According to another aspect of the present invention, there is providedan apparatus comprising: means for acquiring a plurality of proberequest messages originated from a plurality of requesting wirelessapparatuses, each of the plurality of probe request messages comprisingan information element that indicates that each of the plurality ofrequesting wireless apparatuses supports a collision avoidancemechanism; and means for causing, in response to detecting that saidinformation element comprised in the plurality of probe request messagesand indicating said support for the collision avoidance mechanism,transmission of a probe response message that responds to the pluralityof probe request messages.

According to another aspect of the present invention, there is providedan apparatus comprising: means for causing transmission of a proberequest message, wherein the probe request message comprises aninformation element that indicates that the apparatus supports acollision avoidance mechanism that enables a responding wirelessapparatus to reduce a number probe response messages by responding to aplurality of probe response messages with a single probe responsemessage; and means for acquiring a probe response message transmitted bya responding wireless apparatus as a response to the probe requestmessage.

According to yet another aspect of the present invention, there isprovided a computer program product embodied on a computer readabledistribution medium, wherein the computer program product configures aprocessor to execute a computer process comprising: acquiring aplurality of probe request messages originated from a plurality ofrequesting wireless apparatuses, each of the plurality of probe requestmessages comprising an information element that indicates that each ofthe plurality of requesting wireless apparatuses supports a collisionavoidance mechanism; and in response to detecting that said informationelement comprised in the plurality of probe request messages andindicating said support for the collision avoidance mechanism, causingtransmission of a probe response message that responds to the pluralityof probe request messages.

According to yet another aspect of the present invention, there isprovided a computer program product embodied on a computer readabledistribution medium, wherein the computer program product configures aprocessor to execute a computer process comprising: causing transmissionof a probe request message from a requesting wireless apparatus, whereinthe probe request message comprises an information element thatindicates that the requesting wireless apparatus supports a collisionavoidance mechanism that enables a responding wireless apparatus toreduce a number probe response messages by responding to a plurality ofprobe response messages with a single probe response message; andacquiring a probe response message transmitted by a responding wirelessapparatus as a response to the probe request message.

Embodiments of the invention are defined in the dependent claims.

LIST OF DRAWINGS

Embodiments of the present invention are described below, by way ofexample only, with reference to the accompanying drawings, in which

FIG. 1 illustrates an example of a wireless communication scenario towhich embodiments of the invention may be applied;

FIGS. 2 and 3 are signalling diagrams of processes for reducing thenumber of probe responses according to some embodiments of theinvention;

FIG. 4 is a flow diagram of a process for determining the response typein a responding device according to an embodiment of the invention;

FIGS. 5 and 6 are signalling diagrams of processes for enabling arequesting device to determine the type of probe responses according tosome embodiments of the invention;

FIGS. 7 and 8 illustrate block diagrams of apparatuses comprised in therequesting device (FIG. 8) and the responding device (FIG. 7) accordingto some embodiments of the invention; and

FIG. 9 illustrates a signalling diagram for a collision avoidancemechanism according to an embodiment of the invention.

DESCRIPTION OF EMBODIMENTS

The following embodiments are exemplary. Although the specification mayrefer to “an”, “one”, or “some” embodiment(s) in several locations, thisdoes not necessarily mean that each such reference is to the sameembodiment(s), or that the feature only applies to a single embodiment.Single features of different embodiments may also be combined to provideother embodiments. Furthermore, words “comprising” and “including”should be understood as not limiting the described embodiments toconsist of only those features that have been mentioned and suchembodiments may contain also features/structures that have not beenspecifically mentioned.

A general architecture of a wireless communication system to whichembodiments of the invention may be applied is illustrated in FIG. 1.FIG. 1 illustrates groups of wireless communication devices formingwireless networks that may be referred to as basic service sets (BSS). ABSS may be defined by a group of wireless communication devicescomprising an access point (AP) 104, 108 and one or more terminalstations (STA) 110, 112, 114, 116 communicating with the access points104, 108 of their respective groups. A basic service set (BSS) is abasic building block of an IEEE 802.11 wireless local area network(WLAN), and it may have a determined coverage area 100, 102 defined bythe coverage area of the AP 104, 108, for example. The most common BSStype is an infrastructure BSS that includes a single AP together withall associated, non-access-point STAs. The AP may be a fixed AP as AP104, or it may be a mobile AP as AP 108. The APs 104, 108 may alsoprovide access to other networks, e.g. the Internet. In anotherembodiment, at least one of the BSSs, is an independent BSS (IBSS) or amesh BSS (MBSS) without a dedicated AP, e.g. the communication device108 may in such an embodiment be a non-access-point terminal station.While embodiments of the invention are described below in the context ofthe above-described topologies of IEEE 802.11, it should be appreciatedthat other embodiments of the invention are applicable to networks basedon other specifications, e.g. WiMAX (Worldwide Interoperability forMicrowave Access), UMTS LTE (Long-term Evolution for Universal MobileTelecommunication System), and other networks having cognitive radiofeatures, e.g. transmission medium sensing features and capability toadopt operational parameters to enable coexistence with radio accessnetworks based on different specifications and/or standards.

The BSSs are represented by the APs and/or STAs connected to each other,thereby establishing a BSS. Any one of the STAs 110 to 116 may establisha connection to any one of the APs, provided that the BSSs of the APs donot exclude the STAs from their list of devices allowed to connect tothe BSSs, e.g. through shared key processes. In the mesh BSSs and/orindependent BSSs (IBSS), arbitrary connections between devices arepossible. The connection establishment may include authentication inwhich an identity of a STA is established in the AP. The authenticationmay comprise exchanging an encryption key used in the BSS. After theauthentication, the AP and the STA may carry out association in whichthe STA is fully registered in the BSS, e.g. by providing the STA withan association identifier (AID) for frame transmissions.

The 802.11n specifies a data transmission mode in which a STA can haveonly one secondary channel which results in a maximum bandwidth of 40MHz. The primary channel is used in all transmissions, and withassociated devices supporting only the 20 MHz mode. The secondarychannel may be used with clients supporting wider transmissionbandwidths, wherein the primary channel communication is extended byusing the secondary channel as additional bandwidth. A furtherdefinition in 802.11n is that the primary and secondary channels areadjacent. IEEE 802.11ac task group is developing an extension with adata transmission model to provide for wider bandwidths by increasingthe number of secondary channels from 1 up to 7, thus resulting inbandwidths of 20 MHz, 40 MHz, 80 MHz, and 160 MHz.

The primary channel may be used for connection establishment leading toassociation between two wireless apparatuses between which theconnection is to be established. A wireless apparatus preparing for theassociation may scan for channels in order to detect a signal indicatingpresence of another wireless apparatus for association. The wirelessapparatus may be in a completely unassociated state or it may have atleast one existing association while seeking for a new association. IEEE802.11 network discovery mechanisms define two modes: passive and activescanning. In the passive scanning, the wireless apparatus scans achannel for a determined period of time. If a wireless network isdiscovered, the wireless apparatus may proceed to connectionestablishment or, otherwise, it tunes to another channel. The wirelessapparatus may scan for beacon frames, measurement pilot frames, or anyother frames detected. The frames may be originated from any AP ordestined to any AP or, alternatively, the wireless apparatus scans forframes that meet given criteria e.g. a determined identifier, such thatthe wireless apparatus is able to detect any wireless network, includingIBSSs and mesh BSSs. When the wireless apparatus uses the activescanning, it generates probe request frames and transmits them torequest APs or, in general, other wireless apparatuses to reply withprobe response frames. The rules applied to the requesting device (e.g.a STA) and the responding device (e.g. an AP) during the active scanningmay be defined as follows. Upon tuning to a new channel, e.g. a newfrequency channel, the requesting device may first scan the channel fora determined period of time, e.g. a probe delay, or until it detects aframe header, e.g. a physical layer convergence protocol (PLOP) header,on the channel. Thereafter, the requesting device may initiate a channelcontention so as to gain a transmission opportunity for transmission ofa probe request frame. The requesting device may transmit one or moreprobe request frames comprising information (for example, a service setidentifier (SSID) field and/or a BSS identifier field) specifying whichwireless apparatus may respond to the probe request. The requestingdevice may also reset a probe timer to zero and start it upontransmitting the probe request. If the requesting device detects nosignal with sufficiently high energy on the channel on which the proberequest was transmitted before the probe timer reaches a minimum proberesponse time, it tunes to a next channel if any. Otherwise, therequesting device may wait on the channel until the probe timer reachesa maximum probe response time and, thereafter, the requesting deviceprocesses all received probe responses. Optionally, the requestingdevice may then tune to scan the next channel, if any. The probingprocedure provides the requesting device with information on thewireless networks present in the area and, as a consequence, enables therequesting device to select a wireless network with which to establish aconnection. The responding device receiving the probe request mayrespond with a probe response if an address field in the probe requestframe is a broadcast address, an individual medium access control (MAC)address of the responding device, or a multicast address of theresponding device. Another condition may for providing the response isthat the SSID in the probe request is a so-called wildcard SSID, thespecific SSID of the responding device, or the specific SSID of theresponding device is included in an SSID list element of the proberequest. Yet another condition may be that the specific Mesh ID in theprobe request is the specific Mesh ID of the responding device, or anaddress 3 field in the probe request is a wildcard BSSID, the BSSID ofthe responding device, or the MAC address of the peer device in a meshBSS. Further conditions for responding to the probe request may also beset. In general, the probe request specifies the conditions defining thedevices that should respond with the probe response. All devices thatfulfil the conditions may attempt to transmit the probe response frame.

FIG. 2 illustrates an embodiment of the invention for bundling proberesponses so as to reduce signalling traffic in the wireless network ofFIG. 1. FIG. 2 illustrates a flow diagram of a process for responding toa plurality of probe requests. FIG. 2 illustrates steps carried out in arequesting device, e.g. a STA 110 to 116 or even an AP 104, 108, andsteps carried out in a responding device, e.g. an AP 104, 108 or a STA108. As a consequence, it should be appreciated that some embodimentsrealize some aspects of the invention in the responding device, otherembodiments realize other aspects of the invention in the requestingdevice, and yet other embodiments realize yet other aspects of theinvention in a wireless communication system comprising the requestingdevice(s) and the responding device(s). The requesting device(s) and theresponding device(s) may each comprise an apparatus comprising at leastone processor and at least one memory including a computer program code,wherein the at least one memory and the computer program code areconfigured, with the at least one processor, to cause the apparatus tocarry out the process in the requesting/responding device.

Referring to FIG. 2, requesting devices 1 and 2 carry out transmissionof a probe request message in bock 200. Block 200 may be carried outindependently in the requesting devices 1 and 2 and, optionally, inother requesting devices. Depending on the implementation, block 200 maycomprise causing the transmission of the probe request message, e.g.triggering the transmission of the probe request message in therequesting device, or it may comprise also any analog and digital signalprocessing needed prior to emission of radio frequency energy carryingthe probe request from an antenna of the requesting device. In block202, the responding device acquires a plurality of probe requestmessages originated from a plurality of requesting devices, includingthe probe requests transmitted by the requesting devices 1 and 2.Depending on the implementation, block 202 may comprise reception of theprobe request from a radio interface through an antenna of theresponding device and/or any related analog/digital signal processing,or block 202 may comprise acquiring the probe request that has alreadybeen subjected to reception signal processing from a radio receiver or amemory of the responding device. In block 204, the responding devicecarries out transmission of a probe response message comprising aninformation element that indicates whether the probe response message isa probe response to a single probe request message or to a plurality ofprobe request messages. An embodiment of the structure of theinformation element is described in greater detail below but, in short,the information element enables the requesting device to determine fromthe probe response message that is not necessarily addressed directly toit, whether or not the probe response message is still intended to bereceived and extracted by the requesting device. Again, depending on theimplementation block 204 may comprise causing the transmission of theprobe response message, e.g. triggering the transmission of the proberesponse message in the responding device, or it may comprise also anyanalog and digital signal processing needed prior to emission of radiofrequency energy carrying the probe response message from an antenna ofthe responding device.

In block 206, the requesting devices 1 and 2 acquire the probe responsemessage transmitted by a responding device and comprising theinformation element that indicates whether the probe response message isthe probe response to the single probe request message or to theplurality of probe request messages. In block 208, each requestingdevice determines from the information element whether the proberesponse message is the probe response to the single probe requestmessage or to the plurality of probe request messages. If theinformation element indicates that the probe response message is theprobe response to the plurality of request messages, block 208 mayfurther comprise processing, by the requesting device 1, 2, the proberesponse message as a probe response that is related to the proberequest message transmitted by the requesting device 1, 2 in block 200.On the other hand, if the information element indicates that the proberesponse message is the probe response to the single probe requestmessage, at least one of the requesting devices may process the proberesponse message as a probe response that is not related to the proberequest message transmitted in block 200. Further embodiments forprocessing the probe responses are described in greater detail below.

The above-described embodiment of the invention configures theresponding device to respond to a plurality of probe request messageswith a single probe response and to include in the probe responsemessage the information element that indicates whether the proberesponse is a response to a single probe request or multiple proberequests. This reduces the number of probe responses and, thus, thesignalling overhead. Furthermore, the information element enables therequesting devices to determine whether or not they should extract theprobe response, as will be described in greater detail below. Anotheradvantage is that the probability of collisions is reduced as the resultof reduced amount of signalling traffic. Therefore, the embodiments maybe considered as a collision avoidance mechanism. The embodiments alsoenable the devices other than the requesting device(s) to detect thatthe responding device is reducing the number of probe response messages,and this information may be used as measurement statistics in suchdevices.

In an embodiment, the responding device is configured to transmit theprobe response message to a unicast address of one of the requestingdevices, while the other requesting devices may be addressed by theprobe response indirectly through the above-mentioned informationelement, e.g. by setting the information element to indicate that theprobe response is a response to the multiple probe requests. FIG. 3illustrates such a process as an embodiment of the process of FIG. 2.Therefore, steps denoted in FIG. 3 by the same reference numbers as inFIG. 2 represent the same or similar functions. Accordingly, therequesting device(s) transmit the probe requests in block 200, and theresponding device receives/acquires the probe requests in block 202. Inblock 300, the responding device inserts an address of the requestingdevice 1 into a receiver address field of the probe response. Thereceiver address field may be comprised in a medium access control (MAC)header of the probe response message. In the embodiment related to802.11 networks, the address of the requesting device 1 may be added toAddress 1 field. In block 206, the requesting devices 1 and 2 acquirethe probe response message and extract the destination address of theprobe response message. As the probe response message is addressed tothe requesting device 1, the requesting device 1 may process the proberesponse in a conventional manner. Upon detecting that the proberesponse message is addressed to it, the requesting device 1 may extractcontents of the probe response message in block 302.

In an embodiment, the requesting device 1 acknowledges the reception ofthe probe response message by transmitting an acknowledgment message tothe responding device. An advantage in this embodiment is that itenables the responding device to indicate whether it responds to asingle probe request or to multiple probe requests simultaneously andyet it receives, in the form of the acknowledgment message, verificationabout the correct reception of the probe response frame.

However, the requesting device 2 which is not the direct destination ofthe probe response message may process the probe response messageaccording to the following embodiment. Upon detecting that the addressof the requesting device 2 is not comprised in the receiver (MAC)address of the probe response message, the requesting device 2 mayextract the above-mentioned information element so as to determinewhether the probe response message is the response to the single ormultiple probe requests (block 304). It should be appreciated that thesetwo steps may be carried out in a reversed order, e.g. first determiningthe probe response type and then detecting the receiver address. If theinformation element indicates that the probe response message is theprobe response to the multiple probe request messages, the process mayproceed to block 306 in which the requesting device 2 extracts the proberesponse message so as to derive information on the wireless network ofthe responding device from the probe response message. On the otherhand, if the information element indicates that the probe responsemessage is the probe response to the single probe request message, therequesting device 2 may determine that it is not intended to extract theprobe response message, and the requesting device 2 may discard theprobe request message and continue to monitor for the probe responsemessage that is intended to it.

Let us now consider some embodiments related to the format of the proberequest and the probe response and, particularly, to new informationelements included in the probe request and/or the probe response. In anembodiment, the requesting device 1, 2 may include in the probe requestmessage an information element which indicates whether or not therequesting device supports the collision avoidance functionality wherethe responding device responds to multiple probe requests with a singleprobe response. FIG. 9 illustrates an embodiment of such a procedure.Referring to FIG. 9, a requesting device 1, 2 causes transmission of aprobe request message in block 900. The probe request message comprisesan information element that indicates that the requesting wirelessapparatus supports a collision avoidance mechanism where a respondingwireless apparatus reduces a number probe response messages byresponding to a plurality of probe response messages with a single proberesponse message. Both requesting devices and, optionally, otherrequesting devices may carry out block 900 such that the respondingdevice acquires, in block 902, a plurality of probe request messagesoriginated from a plurality of requesting devices, each of the pluralityof probe request messages comprising said information element indicatingthe support for the collision avoidance mechanism. In response todetecting that said information element comprised in the plurality ofprobe request messages and indicating that said plurality of requestingdevice support the collision avoidance, the responding device determinesto execute the collision avoidance mechanism and reduce the number oftransmitted probe response messages. As a consequence, the respondingdevice prepares a probe response message that responds to the pluralityof probe request messages and causes the transmission of the proberesponse message in block 904. In block 906, the requesting device 1, 2acquires the probe response message transmitted by the respondingdevice.

It should be noted that the procedure of FIG. 9 may be independent ofthe procedure of FIG. 2, for example. As a consequence, the indicationof the support for the collision avoidance may be carried out withoutthe responding device providing in the probe response message theinformation element that indicates whether the probe response is theresponse to a single or multiple probe requests. In such embodiments,the responding device may be configured not to explicitly indicatewhether or not it has implemented the collision avoidance mechanism.Such embodiments, however, provide the advantage that the respondingdevice has the option of executing the collision avoidance mechanism ifit considers it feasible. Some criteria for whether or not to executethe collision avoidance are described below. However, in someembodiments, the procedures of FIGS. 2 and 9 are combined to provide anembodiment where the requesting device(s) indicate the support for thecollision avoidance, and the responding device indicates with theinformation element included in the probe response message, whether ornot it implements the collision avoidance mechanism.

The information element indicating the support for the collisionavoidance by the requesting device may be comprised in a collisionavoidance field of the probe request message, and the collisionavoidance field may have the structure shown in Table 1 below.

TABLE 1 Enhanced Scanning Reserved Bit 0 Bits 1-7

The Enhanced Scanning field may be set to 1 or, generally, to a firstvalue to indicate that the requesting device supports the probe responsecollision avoidance, while bit value 0 or, generally, a second valuedifferent from the first value may indicate that the requesting devicedoes not support the probe response collision avoidance. It should beappreciated that the indication of the support of the probe responsecollision avoidance mechanism is not mandatory and, therefore, in someembodiments the requesting devices use conventional probe requestmessages. The support of the collision avoidance of the probe responsesmay be considered by the responding device when deciding the eliminationor combination of the probe responses. When the requesting deviceindicates the support for the probe response collision avoidance, theresponding device may safely apply the collision avoidance mechanism tothose requesting devices that have indicated the support. Even if theEnhanced Scanning field is set to 0 or if the field is not present, theresponding device may still use the collision avoidance mechanism, e.g.it may address the probe response to the unicast address of a requestingdevice not supporting the probe response collision avoidance. In such acase, the requesting device not supporting the collision avoidance mayinterpret the probe response as a conventional probe response, while therequesting device(s) supporting the collision avoidance may process theprobe response as the requesting device 2 in the embodiment of FIG. 3.The other requesting devices not supporting the collision avoidance mayconsider the probe response as not intended to them. The respondingdevice may then send a conventional probe response to such a requestingdevice or devices.

Table 2 below shows an embodiment of the information element inserted inthe probe response message to indicate whether the probe response is aresponse to a single or multiple probe requests.

TABLE 2 Response to Multiple Requests Reserved Bit 0 Bits 1-7

The Respond to Multiple Requests field may be set to 1 or, generally, afirst value to indicate that the probe response message is a response tomultiple probe requests. The probe response may thus contain proberesponses to requesting devices other than that identified by thedestination address in a MAC header of the probe response. Otherwise,the field is set to 0 or, generally, to another value, to indicate thatthe probe response message is the response to a single probe request.

In an embodiment, the responding device may determine whether to respondto a probe request with a dedicated probe response message or to providethe probe response in a beacon frame. When the responding device decidesto use the beacon frame, the responding device may insert into thebeacon frame the following information element instead of that of Table2:

TABLE 3 Response to Beacon Replacing Multiple Requests Probe Response(s)Reserved Bit 0 Bit 1 Bits 2-7

The Beacon Replacing Probe Responses may be set to 1 or, in general afirst value, in the beacon frame to indicate that the beacon framecontains the relevant information elements of the probe response whichis the response to at least one probe request frame. As a consequence,no dedicated probe response will be transmitted for that probe request.Otherwise the field may be set to 0 or, in general a second valuedifferent from the first value. If a probe response frame with Responseto Multiple Requests field set to 1 has been sent during the previousbeacon interval, this field set to 1 for the subsequent beacon frametransmission as well. This enables double verification that an arbitraryrequesting device receives the probe response information. One criterionfor providing the probe response in the beacon frame may be the durationto the next target beacon transmission time (TBTT) when the respondingdevice supports the provision of the probe responses in the beaconframes. For example, if the responding device intends to transmit abeacon frame soon after the probe request, e.g. within the expiry timeof the probe request, the responding device may transmit the beaconframe instead of the dedicated probe response. If the probe requestrequested specific information, the information may be added to thebeacon frame.

In yet another embodiment, the responding device is configured to carryout the collision avoidance mechanism by responding to a single proberequest with a probe response that is combined with another signallingmessage, e.g. the beacon frame. For example, when the responding deviceacquires a probe request a determined time duration before the nextperiodic transmission of the beacon frame, it may choose to insert theprobe response to the beacon frame. The beacon frame may in thisembodiment comprise at least the Beacon Replacing Probe Responseselement of Table 3 so as to enable the requesting device to extract theprobe response from the beacon frame. In this embodiment, the Responseto Multiple Requests element may be omitted or it may be set to indicatethat the probe response is a response to a single probe request.

Let us now consider processing of the probe requests in the respondingdevice according to some embodiments of the invention. FIG. 4illustrates a flow diagram of such a procedure. Referring to FIG. 4, theresponding device acquires at least one probe request originated from arequesting device in block 400. Block 400 may also comprise determiningconditions for the responding device defined in the probe request so asto determine whether or not the responding device is obliged to respondto the probe request. Examples of the conditions have been describedabove. Let us now assume that the responding device fulfils theconditions and, thus, is capable of providing the probe response. Inblock 402, the responding device extracts a receiver address from theprobe request and analyses a type of the receiver address. If thereceiver address of the probe request is an individual address of theresponding device, the process may proceed to block 408 in which theresponding device decides to respond to the probe request with adedicated probe response. As a consequence, the responding device mayinsert into the probe response the information element indicating thatthe probe response is a probe response only to a single probe request.The responding device may then insert into a receiver address field ofthe probe response a MAC address of the requesting device from which theprobe request was originated in block 400. On the other hand, if thereceiver address of the probe request is a multicast address or abroadcast address, the process may proceed to a branch where theresponding device decides to provide a probe response which is a proberesponse to the probe request and to at least one other probe request(block 406). As a consequence, the responding device may implement arule according to which the responding device prefers to respond to aprobe request addressed to a unicast address with the dedicated proberesponse and to respond to a probe request addressed to a multicast orbroadcast address with a probe response that responds to multiple proberequests. The reasoning may be that the responding device determinesfrom the address type of the probe request whether or not there will behigh signalling traffic on the channel of the probe request. If theprobe request is addressed to the unicast address, there will be only asingle probe response, while the probe request addressed to a multicastor broadcast address may cause transmission of a plurality of proberesponses. The probe request and the probe response(s) may be configuredto be transferred on the same channel, e.g. the same frequency channel.

The process of FIG. 4 may proceed directly from block 402 to block 406,if so determined. However, FIG. 4 illustrates another embodiment inwhich the responding device provides an optional step between blocks 402and 406. Block 404 may be applied, if the responding device utilizes asub-process in which the responding device determines whether or not torespond to the probe request addressed to the multicast, broadcastaddress, or group address. In block 404, the responding devicedetermines whether the criteria for omitting the probe response arefulfilled. If the criteria for omitting the response are fulfilled, theprocess proceeds to block 410 in which the responding device omits thetransmission of the probe response. On the other hand, if the criteriafor transmitting the probe response are fulfilled in block 404, theprocess may proceed to block 406. Now, let us consider some examples ofthe criteria the responding device may use in block 404. Depending onthe embodiment, the responding device may consider all the followingcriteria or a subset of them. Similarly depending on the embodiment,when the responding device considers a plurality of criteria, all of thecriteria may need to be fulfilled to proceed to block 410 or only someof the criteria needs to be fulfilled, e.g. at least one criterion. Thecriteria may include at least one of the following criteria: a number ofneighbouring wireless networks detected by the responding device, anumber of other responding devices, a frequency of probe requestreceptions, an amount of traffic on a radio channel, a link qualityassociated with at least one pending probe request, a number of pendingprobe requests, duration from the reception of the probe requestmessage, probability to carry out association for frame transmission asa result of the probe response, and an available capacity of thewireless apparatus.

The responding device may constantly monitor the radio channel anddetect any beacon and/or advertisement signals transmitted byneighbouring wireless networks, e.g. BSSs. For example, if the number ofdetected neighbouring networks is above a given threshold, theresponding device may choose not to respond to every probe request, e.g.it may carry out block 410 for a determined portion of all the receivedprobe requests. The responding device may use this statistical approachto reduce the total number of transmitted probe responses. Theresponding device may also determine the type of the neighbouringwireless networks, e.g. if the number of neighbouring networks that areable to serve the requesting device is above the threshold, theresponding device may carry out block 410 for a determined portion ofthe received probe requests. In general, the responding device mayreduce the number of transmitted probe responses when the criteria aresatisfied, but it may be configured to respond to at least some of thereceived probe requests. The same applies to the frequency of the proberequest receptions, e.g. when the frequency is above a given threshold,the probe responses are reduced. In an embodiment, the criterion is thetotal number of detected probe requests, while in another embodiment thecriterion is the frequency of probe requests concerning the respondingdevice itself. When the number of pending probe requests concerning theresponding device is above a given threshold, the responding device maychoose to reduce the number of transmitted probe responses by providingthe single response to the multiple requests and/or by omitting some ofthe responses.

One criterion may be the number of responses statistically resulting inan association with the responding device. The responding device maymonitor the ratio between the number of probe requests and the number ofassociations. This criterion may be considered from load balancing pointof view, for example. If the ratio is high indicating that a proberesponse is likely to result in a new association and if the availablecapacity of the responding device is low, the responding device maychoose to reduce the number of probe responses.

One criterion may be the cost of the network access, e.g. an operator ofa wireless network provided by the responding device and charging forthe use may prefer that the responding device responds to every proberequest.

One criterion may be the duration from the reception probe request andthe number of detected probe responses to the probe request. Forexample, if the duration from the probe request exceeds a timingthreshold and no probe responses for the probe request have beendetected, the responding device may transmit the probe response. Thisensures that the requesting device receives in time at least one proberesponse that meets the conditions of the probe request.

One criterion may be the quality of the service and/or the radio linkbetween the requesting device and the responding device. This may bedetermined from a reception power of the probe request, for example. Forexample, if there are other responding devices that operate with thesame SSID or, in general, an alternative responding device for proberequest, and if the radio link between the responding device and therequesting device is poor, the responding device may choose not torespond. Similarly, the responding device may choose not to respond, ifthe amount of traffic in the channel is high, e.g. above a threshold.One criterion may relate to the capacity of the responding device andthe type of the current traffic it provides. For example, if thecapacity is low and the current traffic has high quality of service(QoS) demands, the responding device may choose not to respond. Onecriterion of the capacity may also be the capacity of a backbone of theresponding device, e.g. a capacity of a connection from the respondingdevice onwards.

An embodiment configures the responding device to proibide the proberesponse frame as an acknowledgement to the probe request frame. Theresponding device may transmit the probe response to a requesting devicethat has not yet received an acknowledgement or a probe response. Thistype of probe response frame indicates that the responding device hasreceived the probe request and that the requesting device should notretransmit the probe request.

An embodiment provides an alternative response, e.g. as an additionalblock to which the process of FIG. 4 may proceed from block 404. Thealternative response may comprise a response message that signals to therequesting device that the responding device has correctly received theprobe request, e.g. it may be a probe acknowledgment message comprisingless information than the probe response message. In this case, theprobe acknowledgment message addressed to the requesting device mayindicate that the responding device has received the probe request andthat the requesting device should not retransmit the probe request. Theprobe acknowledgment provides a type of reduced probe response message,thus providing the response to a group-addressed probe request and yetreducing the signaling overhead.

In an embodiment, the responding device uses at least some of theabove-mentioned criteria when determining whether to respond to a singleor multiple probe requests with the probe response and/or whendetermining whether to respond with a dedicated probe response or toinclude the probe response in the beacon frame.

In an embodiment, the responding device uses at least some of theabove-mentioned criteria when determining whether to respond with theprobe response to a single or multiple probe requests addressed to aunicast address.

In an embodiment, the responding device prioritizes responses to theprobe requests addressed to unicast addresses over the probe requestsaddressed to multicast, broadcast, or group addresses. Theprioritization may be based on the access categories of the proberequests, e.g. the unicast-addressed probe requests may have a higherpriority than the other probe requests. The responding device may on thebasis of at least one of the above-mentioned criterion decide to reducethe number of probe responses to the multicast, broadcast, or groupaddressed probe requests so as to maintain the higher grade of proberesponses to the unicast-addressed probe requests.

FIG. 5 illustrates an embodiment for enabling the requesting device todetermine from a probe response that is the response to the multipleprobe requests, whether or not the probe response addresses the proberequest the requesting device itself has transmitted. Blocks 200 to 206correspond to those described above. In block 206, the requesting device1, 2 acquires the probe response, and it determines in block 304 whetherthe probe response is a response to multiple probe requests. Let us nowassume that it is. In block 500, the requesting device 1, 2 then carriesout a similar procedure as the responding device does when it evaluateswhether to respond to the probe request or not. The requesting devicechecks in block 500 whether the probe response is from a respondingdevice that matches with the conditions the requesting device defined inthe probe request. For example, the requesting device may compare theaddress and/or SSID included in the conditions defined in the proberequest with the source address and/or SSID included in the proberesponse. If the result of the comparison is a match between theconditions and the probe response, the requesting device may determinethat the probe response is targeted to it and it may extract thecontents of the probe response. On the other hand, if the result of thecomparison is a mismatch between the conditions and the probe response,the requesting device may determine that the probe response is nottargeted to it and it may discard the probe response.

FIG. 6 illustrates another embodiment for enabling the requesting deviceto determine from a probe response that is the response to the multipleprobe requests, whether or not the probe response addresses the proberequest the requesting device itself has transmitted. Blocks 200 to 206and 304 correspond to those described above. Now, the responding deviceinserts into the probe response a list of target devices to which theprobe response is intended (block 600). The list may be provided in theform of a list of MAC addresses of the target devices, but it should beappreciated that any other identifiers may be used instead. Uponreceiving the probe response in block 206 and carrying out block 304,the requesting device 1, 2 may determine from the list of target deviceswhether or not the probe response is intended for the requesting device1, 2 (block 602). If the MAC address or, in general, identifier of therequesting device 1, 2 is contained in the probe response, therequesting device may determine that the probe response is targeted toit and it may extract the contents of the probe response. On the otherhand, if the identifier of the requesting device 1, 2 is not containedin the probe response (block 602), the requesting device may determinethat the probe response is not targeted to it and it may discard theprobe response.

The above-described active scanning procedure involving the proberequests and the probe responses may utilize a QoS enhancement in whichan access category is assigned to the probe request and probe responsemessages. For example, a probe request addressed to a unicast addressand associated probe response may be given a higher priority than aprobe request addressed to a multicast, broadcast, or group address andassociated probe response. In an embodiment, the probe response that isthe response to a multiple probe requests may be categorized as a highpriority message, e.g. when using two priority levels the probe responsemay be assigned with the higher priority level.

FIG. 7 illustrates an embodiment of an apparatus comprising means forcarrying out the above-mentioned functionalities of the wirelessapparatus configured to process received request messages and respond tothen, if so determined. The apparatus of FIG. 7 may thus be consideredas a structural embodiment of the above-mentioned responding device, andit may be comprised in a wireless apparatus. The apparatus may be awireless apparatus of an IEEE 802.11 network or another wirelessnetwork, e.g. an AP. The apparatus may be a computer (PC), a laptop, atablet computer, a cellular phone, a palm computer, a fixed base stationoperating as the AP, or any other wireless apparatus provided with radiocommunication capability. In another embodiment, the apparatus iscomprised in such a wireless apparatus, e.g. the apparatus may comprisea physical circuitry, e.g. a chip, a processor, a micro controller, or acombination of such circuitries in the wireless apparatus.

The apparatus may comprise a communication controller circuitry 10configured to control the communications in the wireless apparatus. Thecommunication controller circuitry 10 may comprise a control part 12handling control signalling communication with respect to transmission,reception, and extraction of control or management frames including theprobe request messages and the probe response messages, as describedabove. The communication controller circuitry 10 may further comprise adata part 16 that handles transmission and reception of payload dataduring transmission opportunities of the wireless apparatus(transmission) or transmission opportunities of other wirelessapparatuses (reception). The communication controller circuitry 10 mayfurther comprise a request processor circuitry 15 configured to carryout at least some of the request processing procedures described above.The request processor circuitry 15 may be configured to acquire a proberequest message through the control part 12 and to process the proberequest message so as to determine whether or not to respond to theprobe request and/or the type of the probe response message to be used.For the former purpose, the request processor circuitry 15 may comprisea response trigger circuitry 18 configured to assess at least some ofthe above-mentioned conditions and/or criteria so as to determinewhether or not the preparation of the probe response should betriggered. Upon determining that the probe request should be respondedwith the probe response, the response trigger circuitry 18 may beconfigured to trigger the preparation of the probe response message bycalling a response bundler circuitry 14 to carry out the preparation ofthe probe response message. The response bundler circuitry 14 may beconfigured to determine whether to respond to only one probe request orto respond to multiple probe requests with a single probe response.Depending on the decision, the response bundler circuitry 14 mayconfigure the control part 12 to prepare a probe response comprising theabove-mentioned information element of Table 2 or 3 indicating the typeof the probe response message. The control part 12 may then determinewhether to transmit the probe response as the dedicated probe responsemessage or to include the probe response in a beacon frame or anotherperiodically transmitted control frame.

The circuitries 12 to 18 of the communication controller circuitry 10may be carried out by the one or more physical circuitries orprocessors. In practice, the different circuitries may be realized bydifferent computer program modules. Depending on the specifications andthe design of the apparatus, the apparatus may comprise some of thecircuitries 12 to 18 or all of them.

The apparatus may further comprise a memory 20 storing computer programs(software) configuring the apparatus to perform the above-describedfunctionalities of the wireless apparatus. The memory 20 may also storecommunication parameters and other information needed for the wirelesscommunications, e.g. the rules for determining whether or not to respondto multiple probe requests with a single probe response. The apparatusmay further comprise radio interface components 22 providing theapparatus with radio communication capabilities within its wirelessnetwork and/or with other wireless networks. The radio interfacecomponents 22 may comprise standard well-known components such asamplifier, filter, frequency-converter, (de)modulator, andencoder/decoder circuitries and one or more antennas. The apparatus mayfurther comprise a user interface enabling interaction with the user ofthe communication device. The user interface may comprise a display, akeypad or a keyboard, a loudspeaker, etc.

In an embodiment, the apparatus carrying out embodiments of theinvention in the wireless apparatus comprises at least one processor andat least one memory including a computer program code, wherein the atleast one memory and the computer program code are configured, with theat least one processor, to cause the apparatus to carry out thefunctionality of the responding device in any one of the processes ofFIGS. 2 to 6 and 9. Accordingly, the at least one processor, the memory,and the computer program code form processing means for carrying outembodiments of the present invention in the wireless communicationapparatus processing request messages.

FIG. 8 illustrates an embodiment of an apparatus comprising means forcarrying out the above-mentioned functionalities of the requestingdevice configured to carry out an active scanning process involving therequest messages and response messages. The apparatus may be a wirelessapparatus of an IEEE 802.11 network or another wireless network, e.g. aSTA. The apparatus may be a computer (PC), a laptop, a tablet computer,a cellular phone, a palm computer, or any other apparatus provided withradio communication capability. In another embodiment, the apparatus iscomprised in such a wireless apparatus, e.g. the apparatus may comprisea physical circuitry, e.g. a chip, a processor, a micro controller, or acombination of such circuitries in the wireless apparatus.

The apparatus may comprise a communication controller circuitry 50configured to control the communications in the wireless apparatus. Thecommunication controller circuitry 50 may comprise a control part 52handling control signalling communication with respect to transmission,reception, and extraction of control or management frames including therequest messages and the response messages, as described above. Thecommunication controller circuitry 50 may further comprise a data part56 that handles transmission and reception of payload data duringtransmission opportunities of the wireless apparatus (transmission) ortransmission opportunities of other wireless apparatuses (reception).The communication controller circuitry 50 may further comprise an activescanning controller circuitry 55. The active scanning controllercircuitry 55 may comprise a request trigger circuitry 58 configured totrigger the active scanning procedure. As a consequence, the requesttrigger circuitry 58 may trigger the control part 52 to prepare theabove-described probe request message. The control part 52 may theninclude in the probe request message the information element of Table 1.After transmitting the probe request, the control part 52 may monitorfor probe response messages and, upon detecting a probe responsemessage, the control part may forward the detected probe responsemessage to a response identifier circuitry 54. Upon acquiring the proberesponse message, the response identifier circuitry 54 may determinewhether or not the probe response message is a probe response to thetransmitted probe request message according to any one of theabove-described embodiments (block 208, 304, 306, 500, 602). Uponacquiring the verification that the probe response message is the proberesponse to the transmitted probe request message, the active scanningcontroller circuitry 55 may extract the contents of the probe responsemessage. Otherwise, it may discard the probe response message.

The circuitries 52 to 58 of the communication controller circuitry 50may be carried out by the one or more physical circuitries orprocessors. In practice, the different circuitries may be realized bydifferent computer program modules. Depending on the specifications andthe design of the apparatus, the apparatus may comprise some of thecircuitries 52 to 58 or all of them.

The apparatus may further comprise a memory 60 to store computerprograms (software) configuring the apparatus to perform theabove-described functionalities of the requesting device. The memory 60may also store communication parameters and other information needed forthe wireless communications, e.g. the rules for processing the requestand response messages. The apparatus may further comprise radiointerface components 62 providing the apparatus with radio communicationcapabilities within the BSS and/or with other BSSs. The radio interfacecomponents 62 may comprise standard well-known components such asamplifier, filter, frequency-converter, (de)modulator, andencoder/decoder circuitries and one or more antennas. The apparatus mayfurther comprise a user interface enabling interaction with the user ofthe communication device. The user interface may comprise a display, akeypad or a keyboard, a loudspeaker, etc.

In an embodiment, the apparatus carrying out the embodiments of theinvention in the wireless apparatus comprises at least one processor andat least one memory including a computer program code, wherein the atleast one memory and the computer program code are configured, with theat least one processor, to cause the apparatus to carry out thefunctionality of the requesting device 1, 2 in any one of the processesof FIGS. 2, 3, 5, 6, and 9. Accordingly, the at least one processor, thememory, and the computer program code form processing means for carryingout embodiments of the present invention in the apparatus functioning inthe requesting device.

As used in this application, the term ‘circuitry’ refers to all of thefollowing: (a) hardware-only circuit implementations such asimplementations in only analog and/or digital circuitry; (b)combinations of circuits and software and/or firmware, such as (asapplicable): (i) a combination of processor(s) or processor cores; or(ii) portions of processor(s)/software including digital signalprocessor(s), software, and at least one memory that work together tocause an apparatus to perform specific functions; and (c) circuits, suchas a microprocessor(s) or a portion of a microprocessor(s), that requiresoftware or firmware for operation, even if the software or firmware isnot physically present.

This definition of ‘circuitry’ applies to all uses of this term in thisapplication. As a further example, as used in this application, the term“circuitry” would also cover an implementation of merely a processor (ormultiple processors) or portion of a processor, e.g. one core of amulti-core processor, and its (or their) accompanying software and/orfirmware. The term “circuitry” would also cover, for example and ifapplicable to the particular element, a baseband integrated circuit orapplications processor integrated circuit (ASIC) for the apparatusaccording to an embodiment of the invention.

The processes or methods described in FIGS. 2 to 6 and 9 may also becarried out in the form of a computer process defined by a computerprogram. The computer program may be in source code form, object codeform, or in some intermediate form, and it may be stored in some sort ofcarrier, which may be any entity or device capable of carrying theprogram. Such carriers include transitory and/or non-transitory computermedia, e.g. a record medium, computer memory, read-only memory,electrical carrier signal, telecommunications signal, and softwaredistribution package. Depending on the processing power needed, thecomputer program may be executed in a single electronic digitalprocessing unit or it may be distributed amongst a number of processingunits.

The present invention is applicable to wireless communication systemsdefined above but also to other suitable communication systems. Theprotocols used, the specifications of wireless communication systems,their network elements and terminals, develop rapidly. Such developmentmay require extra changes to the described embodiments. Therefore, allwords and expressions should be interpreted broadly and they areintended to illustrate, not to restrict, the embodiment. It will beobvious to a person skilled in the art that, as technology advances, theinventive concept can be implemented in various ways. The invention andits embodiments are not limited to the examples described above but mayvary within the scope of the claims.

1. A method comprising: acquiring, in a wireless apparatus a pluralityof probe request messages originated from a plurality of requestingwireless apparatuses, each of the plurality of probe request messagescomprising an information element that indicates that each of theplurality of requesting wireless apparatuses supports a collisionavoidance mechanism; in response to detecting that said informationelement comprised in the plurality of probe request messages andindicating said support for the collision avoidance mechanism, causingtransmission of a probe response message that responds to the pluralityof probe request messages.
 2. The method of claim 1, wherein the proberesponse message comprises an information element that indicates whetherthe probe response message is a probe response to a single probe requestmessage or to a plurality of probe request messages.
 3. The method ofclaim 1, further comprising: addressing the probe response message to aunicast address of a requesting wireless apparatus.
 4. The method ofclaim 1, further comprising: determining whether or not at least some ofthe probe request message are addressed to a broadcast address, amulticast address, or a unicast address; if the probe request messageaddressed to the broadcast address or the multicast address aredetected, causing transmission of said probe response message that isthe probe response to the plurality of probe request messages; and ifthe probe request message is addressed to the unicast address, causingtransmission of a probe response message that is the probe response to asingle probe request message. 5-8. (canceled)
 9. A method comprising:causing, in a requesting wireless apparatus, transmission of a proberequest message from the requesting wireless apparatus, wherein theprobe request message comprises an information element that indicatesthat the requesting wireless apparatus supports a collision avoidancemechanism that enables a responding wireless apparatus to reduce anumber probe response messages by responding to a plurality of proberesponse messages with a single probe response message; and acquiring,in the requesting wireless apparatus, a probe response messagetransmitted by a responding wireless apparatus as a response to theprobe request message.
 10. The method of claim 9, wherein the proberesponse message comprises an information element that indicates whetherthe probe response message is a probe response to a single probe requestmessage or to a plurality of probe request messages; and if theinformation element indicates that the probe response message is theprobe response to the plurality of request messages, processing theprobe response message as a probe response that is related to thetransmitted request message; and if the information element indicatesthat the probe response message is the probe response to the singleprobe request message, processing the probe response message as a proberesponse that is not related to the transmitted request message.
 11. Themethod of claim 10, further comprising: if the information elementindicates that the probe response message is the probe response to theplurality of request messages, extracting information on a wirelessnetwork from the probe response message; and if the information elementindicates that the probe response message is the probe response to thesingle probe request message, discarding the probe request message andcontinuing to monitor for the probe response message that is related tothe transmitted request message.
 12. The method of claim 9, wherein theprobe response message is addressed to a unicast address of anotherrequesting wireless apparatus, a broadcast address, or a multicastaddress. 13-16. (canceled)
 17. An apparatus comprising: at least oneprocessor; and at least one memory including program instructions,wherein the at least one memory and the computer program code areconfigured, with the at least one processor, to cause the apparatus toacquire a plurality of probe request messages originated from aplurality of requesting wireless apparatuses, each of the plurality ofprobe request messages comprising an information element that indicatesthat each of the plurality of requesting wireless apparatuses supports acollision avoidance mechanism; in response to detecting said informationelement comprised in the plurality of probe request messages andindicating said support for the collision avoidance mechanism, causetransmission of a probe response message that responds to the pluralityof probe request messages.
 18. The apparatus of claim 17, wherein theprobe response message comprises an information element that indicateswhether the probe response message is a probe response to a single proberequest message or to a plurality of probe request messages.
 19. Theapparatus of claim 17, wherein the at least one memory and the computerprogram code are configured, with the at least one processor, to causethe apparatus to address the probe response message to a unicast addressof a requesting wireless apparatus.
 20. The apparatus of claim 17,wherein the at least one memory and the computer program code areconfigured, with the at least one processor, to cause the apparatus to:determine whether or not at least some of the probe request message areaddressed to a broadcast address, a multicast address, or a unicastaddress; if the probe request message addressed to the broadcast addressor the multicast address are detected, cause transmission of said proberesponse message that is the probe response to the plurality of proberequest messages; and if the probe request message is addressed to theunicast address, cause transmission of a probe response message that isthe probe response to a single probe request message. 21-22. (canceled)23. The apparatus of claim 17, wherein the at least one memory and thecomputer program code are configured, with the at least one processor,to cause the apparatus to provide the probe response message in the formof a periodically transmitted beacon frame instead of a dedicated proberesponse frame.
 24. The apparatus of claim 17, wherein the at least onememory and the computer program code are configured, with the at leastone processor, to cause the apparatus to: determine on the basis ofpending probe requests, a set of requesting wireless apparatuses to beprovided with a probe response; and insert into the probe responsemessage a list of identifiers associated with the determined requestingwireless apparatuses to which the probe response message is targeted.25. An apparatus comprising: at least one processor; and at least onememory including program instructions, wherein the at least one memoryand the computer program code are configured, with the at least oneprocessor, to cause the apparatus to: cause transmission of a proberequest message, wherein the probe request message comprises aninformation element that indicates that the apparatus supports acollision avoidance mechanism that enables a responding wirelessapparatus to reduce a number probe response messages by responding to aplurality of probe response messages with a single probe responsemessage; and acquiring a probe response message transmitted by theresponding wireless apparatus as a response to the probe requestmessage.
 26. The apparatus of claim 25, wherein the probe responsemessage comprises an information element that indicates whether theprobe response message is a probe response to a single probe requestmessage or to a plurality of probe request messages, and wherein the atleast one memory and the computer program code are configured, with theat least one processor, to cause the apparatus to: if the informationelement indicates that the probe response message is the probe responseto the plurality of request messages, process the probe response messageas a probe response that is related to the transmitted request message;and if the information element indicates that the probe response messageis the probe response to the single probe request message, process theprobe response message as a probe response that is not related to thetransmitted request message.
 27. The apparatus of claim 26, wherein theat least one memory and the computer program code are configured, withthe at least one processor, to cause the apparatus to: if theinformation element indicates that the probe response message is theprobe response to the plurality of request messages, extract informationon a wireless network from the probe response message; and if theinformation element indicates that the probe response message is theprobe response to the single probe request message, discard the proberequest message and continuing to monitor for the probe response messagethat is related to the transmitted request message.
 28. The apparatus ofclaim 25, wherein the probe response message is addressed to a unicastaddress of another requesting wireless apparatus, a broadcast address,or a multicast address.
 29. (canceled)
 30. The apparatus of claim 25,wherein the at least one memory and the computer program code areconfigured, with the at least one processor, to cause the apparatus to:insert into the probe request message at least one criterion that aresponding wireless apparatus must satisfy in order to transmit saidprobe response message; if the information element indicates that theprobe response message is the probe response to the plurality of requestmessages, determine from contents of the probe request message whetheror not it provides a match with said at least one criterion; if theprobe response message provides a match with said at least onecriterion, process the probe response message as a probe response thatis related to the transmitted request message; and if the probe responsemessage does not provide a match with said at least one criterion,process the probe response message as a probe response that is notrelated to the transmitted request message.
 31. The apparatus of claim25, wherein the probe response message comprises a list of identifiersassociated with requesting wireless apparatuses to which the proberesponse message is targeted, if the probe response message is the proberesponse to the plurality of request messages, and wherein the at leastone memory and the computer program code are configured, with the atleast one processor, to cause the apparatus to: check for the presenceof an identifier of the requesting wireless apparatus in the proberesponse message; if the probe response message comprises an identifierof the requesting wireless apparatus, process the probe response messageas a probe response that is related to the transmitted request message;and if the probe response message does not comprise the identifier ofthe requesting wireless apparatus, process the probe response message asa probe response that is not related to the transmitted request message.32. The apparatus of claim 25, wherein the at least one memory and thecomputer program code are configured, with the at least one processor,to cause the apparatus to acquire the probe response comprised in aperiodic beacon frame.